The Influence of the Arsine Source on the Purity of InGaAs Grown by Hydride VPE

ABSTRACTThe relatively high background carrier concentration obtained in unintentionally doped epitaxial layers of III-V materials imposes a limitation on applications of the hydride VPE process. It is usually attributed to impurities in the gas sources. Results are presented for InGaAs grown by hydride VPE using a range of growth conditions. Carrier concentrations and growth rates for the various samples were determined using, respectively, Polaron electrochemical profiler measurements and scanning electron microscopy. It is shown that the observed background carrier concentration increased with increasing input mole fraction of arsine under conditions of constant growth rate. This strongly implicates the arsine feed gas as a predominant source of impurity. Attempts to purify the arsine feed gas using sodium alumina-silicate molecular sieves are described. Polaron electrochemical profiler measurements and Hall effect measurements on samples grown both with and without molecular sieves in the arsine feed line are presented. From a comparison of the corresponding values of carrier concentration and mobility it is shown that Type 4A molecular sieves were not effective in removing dopant impurities from the 4% arsine-hydrogen mixture used.